superkgd: the gd future of superkamiokande · 2019. 8. 13. · 2 super-kamiokande detector 50 kton...

SuperKGd: the Gd future of

SuperKamiokande

Lluís Martí Magro, ICRR36th ICRC July 31st, 2019. Madison, WI, USA

2

Super-Kamiokande Detector 50 kton water ~2 m OD viewed by

8-inch PMTs 32 kt ID viewed by

20-inch PMTs Trigger efficiency:

>99%@3.5 MeV Ekin

Electronics hutLINAC

Control room

Water and air purification system

SK

2km3km

1km(2700mwe)

39.3m

41.4m

Atotsuentrance

AtotsuMozumi

Ikeno-yamaKamioka-cho, Gifu

ID

OD

Phase SK-I SK-II SK-III SK-IV SK-VStart -end

1996 Apr -2001 Jul

2002 Oct - 2005 Oct

2006 Jul - 2008 Sep

2008 Sep - 2018 Mar

2019 Jan 29-

Number of

PMTs

ID(coverage)

11146(40 %)

5182 (19 %)

11129(40 %)

11129(40 %)

11129(40%)

OD 1885 1885

3

Super-Kamiokande DetectorElectronics hutLINAC

Control room

Water and air purification system

SK

2km3km

1km(2700mwe)

39.3m

41.4m

Atotsuentrance

AtotsuMozumi

Ikeno-yamaKamioka-cho, Gifu

ID

OD

Phase SK-I SK-II SK-III SK-IV SK-VStart -end

1996 Apr -2001 Jul

2002 Oct - 2005 Oct

2006 Jul - 2008 Sep

2008 Sep - 2018 Mar

2019 Jan 29-

Number of

PMTs

ID(coverage)

11146(40 %)

5182 (19 %)

11129(40 %)

11129(40 %)

11129(40%)

OD 1885 1885

Versatile detector:Solar neutrinosAtmospheric neutrinosProton decaySupernovaeSupernova Relic NeutrinosIndirect search for DMand more

Low energy event reconstruction

+ e- → + e-Solar neutrino:

Reconstruction:

- Interaction vertex: ⇨Timing information

- Electron direction: ⇨Cherenkov Ring pattern

- Electron energy: ⇨Number of hit PMTs, Neff (~6 hit/MeV @ SK-I, III and IV)

Resolution (10 MeV electron case): → Energy 14% Vertex: 87 cm Direction: 26° → Energy 14% Vertex: 55 cm Direction: 23° Software improvement

for SK-III & SK-IV

SK-I

4

Neutron tagging in pure water

5

p

n

e+42º

(Not efficiently detected, no neutron tagging used)

γ (2.2 MeV)p

Pure watere

DT ~ 200 ms

Neutron tagging in Gd loaded water

6

p

n

e+42º

(Not efficiently detected, no neutron tagging used)

γ (2.2 MeV)p

Pure watere

DT ~ 200 ms

γ

ep

n

Gd

e+

8 MeV gamma cascade42º

Gd-loaded water

DT ~ 30 ms

With tight time (delayed) and position coincidence between positron and neutron capture (90% neutron capture on Gd with 0.2% Gd2(SO4)3 concentration) we will be able to tag neutrons with high efficiency

Idea proposed as GADZOOKS!by Beacom & Vagins PRL.93, (2004) 171101

7

Supernova Relic NeutrinosSupernova relic neutrinos (SRN) are those neutrinos from all the past core collapse supernovae in the history of the universe.

Phys.Rev. D 79, 08013 (2009)Phys.Rev. D85 (2012) 052007

From the predictions for the SRN spectrum there should be a discovery window between reactor and atmospheric neutrinosSo far, irreducible backgrounds seriously limited the analysis

8

Other benefits from GdCore-collapse burst: gadolinium will allow us neutrino tagging, i.e. identify the dominant IBD events:

- Prompt recognition of a SN - This would outline the νx elastic scattering: νx + e- → νx + e- and

hence greatly improves the pointing accuracy to the SN- Measure νe and νe spectra

Pre-burst (nearby) signal: for M > 8 M⊙ during Si burning

NO IO

The road to SuperKGd: EGADS200-ton detector with 240 photomultipliers

Dissolution and pre-treatment system

Selective band-pass filtration system

Water Transpare

ncy measuremen

t

EGADS was build using the same materials as in SuperKBecause of all the exciting possibilities, in June 2009 the SK collaboration launched the EGADS project

Evaluating Gadolinium's Action on Detector Systems

The road to SuperKGd: EGADS200-ton detector with 240 photomultipliers

Dissolution and pre-treatment system

Selective band-pass filtration system

Water Transpare

ncy measuremen

t

EGADS was build using the same materials as in SuperKBecause of all the exciting possibilities, in June 2009 the SK collaboration launched the EGADS project


Our Goals:✔ Water purification system✔ Monitor the water transparency✔ Effects on detector components✔ Adding/removing Gd✔ Neutron background

11

- 0.2 % Gd sulfate is as transparent to Cherenkov light as pure-water- Our water system achieves this with no Gd losses- Gd concentration is homogeneous in our detector

EGADS’ main result

12

Refurbishment work: Clean walls and detector structures and remove potential sources of rust Replace faulty ID and OD PMTs Replace the OD white Tyvek

Upgrade: New hall excavated for the new Gd water system Modify the intank piping

SuperKamiokande upgrade

Thank you all for the hard work !!

13

SuperKamiokande refurbishment

Walls, structure & floor cleaned

Damaged parts recovered

Special care of not leaving any pieces/tools behind

14

SuperKamiokande ID PMT refurbishment

~ 140 ID PMTs replaced or connections checked/redone.

15

- Newly developed Hamamatsu HQE B&L PMT with high QE- x2 better single photon efficiency as compared to the SuperK PMTs

SuperKamiokande ID PMT refurbishment

Improved charge and timing resolutions (see backup)

16

SuperKamiokande OD PMT refurbishment

~200 OD PMTs are replaced (~100 on the top)

SuperKamiokande Tyvek refurbishment

B-W and W-W Tyvek replacement17

18

Old piping scheme (until SK-IV)

60 tons/h cleaning powerNo control on OD fluxNo control on individual valves


19


OD/ID independent flux + top&bottom independent flux in the outer

Current flow (SK-V)



20


Increased cleaning power to 120 ton/hOD/ID independent flux + top&bottom independent flux in the outer

Approximate flow for SK-Gd



21

SuperKamiokande refurbishment

22

SuperKamiokande refurbishmentWe do not observe any water leak within the accuracy of our measurement, which is less than 0.017 tons per day. This is less than 1/200th of the leak rate observed before the 2018/9 tank refurbishment.

23

Preparation of Gd sulfate and water system until end of 2019Running with new water system from end 2019Gd sulfate dissolution by March 2020Commissioning (3 months and calibrations ~2-3 months)

First steps in SKGd: timeline

Summary

24

Neutron tagging can be used in basically all analyses at SK and adding 0.2% of Gd sulfate will give us this capability

EGADS has shown it is feasible: we can remove impurities and maintain high transparency water, with basically no Gd losses, etc.

Refurbishment work at SK done:- Detector structure and walls were refurbished- Faulty OD and ID PMTs replaced. - Water leak currently undetectable- Piping upgraded

Preparing for the first Gd loading until end of this year and dissolving in early 2020.

Exciting physics days ahead with neutron tagging at SuperK-Gd !!

25

Careful work and early water cleaning allowed for a fast water transparency recovery after refurbishment.

SuperKamiokande water transparency

26

Hyper-Kamiokande ID photo-sensors- Newly developed Hamamatsu HQE B&L PMT with high QE- x2 better single photon efficiency as compared to the SuperK PMTs- Improved charge and timing resolutions

50-cm HQE B&L R12860

Single PE

SK HKPV ~2 ~4Resol. 50% 35%

SK HKRise [ns] 10.6 6.7FWHM [ns] 18.5 13

27

New Water System for SuperKGd

Nov 2016 Nov 2016

EGADS

28


EGADS

March 2017

March 2017

Cavern for the new water system has been excavated

Equipment has been already installed (Gd solution, etc)

29


30

Currently we do not observe any water leakage from the SK tank within the accuracy of our measurement, which is less than 0.017 tons per day. This is less than 1/200th of the leak rate observed before the 2018/2019 tank refurbishment.

There was no drop in the water level (no leak). The rise of ~0.1 mm observed at 8:27 on February 4 and 14:30 on February 7, respectively, is consistent with the prediction due to the volumetric expansion of water from heat inflow.

SuperKamiokande leak status

31

Relevant radioactive contamination, typical impurities in untreated Gd sulfate and our requirements from our physics goals:

Backgrounds

Chain Part of the chainTypical

(mBq/Kg)SRN

(mBq/Kg)Solar

(mBq/Kg)

238U238U

226Ra 50 5

< 5 -

- < 0.5

232Th232Th228Th

10 100

- -

< 0.05 < 0.05

235U235U

227Ac/227Th 32 300

- -

< 3 < 3

32

We plan to use resins AJ4400 and AJ1020 to further remove U and Ra after dissolving Gd sulfate

Backgrounds

Chain Part of the chainTypical

(mBq/Kg)SRN

(mBq/Kg)Solar

(mBq/Kg)

238U238U

226Ra 50 5

< 5 -

- < 0.5

232Th232Th228Th

10 100

- -

< 0.05 < 0.05

235U235U

227Ac/227Th 32 300

- -

< 3 < 3

CompanyA

CompanyB

CompanyC

< 0.04 < 0.2

< 0.04 < 0.2

< 0.04 ~ 1

0.02 < 0.3

0.06 < 0.26

0.09 ~ 2

< 0.4 < 1.5

< 0.3 < 1.2

< 1.3 < 3.1

Measurements done at Canfranc, Boulby and KamiokaCompany names hidden

Relevant radioactive contamination, typical impurities in untreated Gd sulfate and our requirements from our physics goals:

The road to SuperKGd: EGADSBecause of all the exciting possibilities, in June 2009 the SuperK collaboration launched the EGADS project


Super-K Water system

５０ｍ

EGADS Hall(2500 m3)

Super-KamiokandeOur Goals:✔ Water purification system✔ Monitor the water transparency✔ Effects on detector components✔ Adding/removing Gd✔ Neutron background

Soaked Mine-guard-C in Gd loaded water with good results: Cherenkov ilght loss in 15 m is 77.64 % (well within the typical SK-III SK-IV values)

MineguardC soak tests

34

Sampling positions at 1660 mm, 3320 mm and 4990 mm from top of the tank (for water transparency, UDEAL, and Gd concentration measurements)

EGADS detector

6025

mm

to water system

from water system

1326

mm

240 PMTs were installed in summer 2013

35

Atmospheric ν backgrounds

36

● Charge Current:

e+

n

m

nnm

e

m

nnm

e

T < 50 MeV

Invisible m:

m generation:

ne

ne CC

● Neutral Current:

ng

16O*

NC elastic

Total BGNC elastic

ne CCnm CC

Total Energy [MeV]

Background vs expected signal

37

Total Energy [MeV]

SRN flux:Horiuchi, Beacom, DwekPRD, 79, 083013 (2009)

SRN number of expected events after 10 years of observation

The detection of SRN depends on the typical SN emission spectrum

Tn~5 (MNS/1.4M⦿)1/3 (RNS/10km)-3/4

With SuperK-Gd the first SRN observation is within our reach!!

Step 4: EGADS Detector

- Step 1: Circulation through the 200 ton tank with pure water (first half 2011 pure water circulation) Done!- Step 2: Circulation through the 15 ton tank with Gd2(SO4)3 (from middle 2011 to end 2012) Done!- Step 3: Circulation though the 200 ton tank with Gd2(SO4)3 Done!- Step 4: PMT mounting (240 in total). Done!- Step 5: Full realization of the EGADS project Done!

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superkgd: the gd future of superkamiokande · 2019. 8. 13. · 2 super-kamiokande detector 50 kton...

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